Tetrahydroisoquinoline derivatives as modulators of dopamine D3 receptors

ABSTRACT

Compounds of formula (I): 
                 
 
wherein:
         R 2  represents a hydrogen atom or a C 1-4 alkyl group;   q is 1 or 2;
           A represents a group of formula (a) or (b) 
                 
 
wherein
   
           T, U, V and Y independently represent CH or a nitrogen atom;   R 5  is a group selected from: a hydrogen or halogen atom, cyano, C 1-4  alkyl or C 1-4  alkoxy group   s is 1 or 2;   Ar 2  represents an optionally substituted phenyl ring or an optionally substituted 5- or 6-membered aromatic heterocyclic ring; and salts thereof. The compounds are useful for the treatment of conditions which require modulaton of a dopamine receptor such as schizophrenia.

This is a continuation of application Ser. No. 09/719,146 filed Dec. 7, 2000, now abandoned, which is a 371 national phase application of PCT/EP99/03840, filed Jun. 1, 1999.

The present invention relates to novel tetrahydroisoquinoline derivatives, processes for their preparation, pharmaceutical compositions containing them and their use in therapy, as modulators of dopamine D₃ receptors, in particular as antipsychotic agents.

U.S. Pat. No. 5,294,621 describes tetrahydropyridine derivatives of the formula:

wherein

is an optionally substituted thienyl or optionally substituted phenyl ring; R¹, R² and R³ are each inter alia hydrogen; X is inter alia (CH₂)mNR⁷CO; m is 2-4; and Ar¹ is an optionally substituted heterocyclic ring or an optionally substituted phenyl ring. The compounds are said to be useful as antiarrhythmic agents.

EPA 431,580 describes compounds of formula

wherein R is OR³, NR⁴R⁵, or N(OR⁴)R⁵, R⁴ and R⁵ are inter alia hydrogen, lower alkyl, aroyl or heteroaroyl; m is zero, 1 or 2; R¹ is hydrogen, aryl or various heteroaryl groups; n is zero or 1-4; and R² is:

The compounds are said to be dopaminergic agents useful as antipsychotics, antihypertensives and also of use in the treatment of hyperprolactinaemia-related conditions and several central nervous system disorders.

WO 95/10513 describes benzothiophene derivatives and related compounds as estrogen agonists.

We have now found a class of tetrahydroisoquinoline derivatives which have affinity for dopamine receptors, in particular the D₃ receptor, and thus potential in the treatment of conditions wherein modulation of the D₃ receptor is beneficial, eg as antipsychotic agents.

In a first aspect the present invention provides compounds of formula (I):

wherein:

-   -   R¹ represents a substituent selected from: a hydrogen or halogen         atom; a hydroxy, cyano, nitro, trifluoromethyl,         trifluoromethoxy, trifluoromethanesulfonyloxy, pentafluoroethyl,         C₁₋₄alkyl, C₁₋₄alkoxy, arylC₁₋₄alkoxy, C₁₋₄alkylthio,         C₁₋₄alkoxyC₁₋₄alkyl, C₃₋₆cycloalkylC₁₋₄alkoxy, C₁₋₄alkanoyl,         C₁₋₄alkoxycarbonyl, C₁₋₄alkylsulfonyl, C₁₋₄alkylsulfonyloxy,         C₁₋₄alkylsulfonylC₁₋₄alkyl, arylsulfonyl, arylsulfonyloxy,         arylsulfonylC₁₋₄alkyl, C₁₋₄alkylsulfonamido, C₁₋₄alkylamido,         C₁₋₄alkylsulfonamidoC₁₋₄alkyl, C₁₋₄alkylamidoC₁₋₄alkyl,         arylsulfonamido, arylcarboxamido, arylsulfonamidoC₁₋₄alkyl,         arylcarboxamidoC₁₋₄alkyl, aroyl, aroylC₁₋₄alkyl, or         arylC₁₋₄alkanoyl group; a group R³OCO(CH₂)_(p),         R³CON(R⁴)(CH₂)_(p), R³R⁴NCO(CH₂)_(p) or R³R⁴NSO₂(CH₂)_(p) where         each of R³ and R⁴ independently represents a hydrogen atom or a         C₁₋₄alkyl group or R³R⁴ forms part of a C₃₋₆azacyloalkane or         C₃₋₆(2-oxo)azacycloalkane ring and p represents zero or an         integer from 1 to 4; or a group Ar¹—Z, wherein Ar¹ represents an         optionally substituted phenyl ring or an optionally substituted         5- or 6-membered aromatic heterocyclic ring and Z represents a         bond, O, S , or CH₂;     -   R² represents a hydrogen atom or a C₁₋₄alkyl group;     -   q is 1 or 2;         A represents a group of formula (a) or (b):         wherein     -   T, U, V and Y independently represent CH or a nitrogen atom;     -   R⁵ is a group selected from: a hydrogen or halogen atom, cyano,         C₁₋₄ alkyl or C₁₋₄ alkoxy group     -   s is 1 or 2.     -   Ar² represents an optionally substituted phenyl ring or an         optionally substituted 5- or 6-membered aromatic heterocyclic         ring     -   and salts thereof.

In the compounds of formula (I) above an alkyl group or moiety may be straight or branched. Alkyl groups which may be employed include methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl and any branched isomers thereof such as isopropyl, t-butyl, sec-butyl, and the like.

When R¹ represents an arylC₁₋₄alkoxy, arylsulfonyl, arylsulfonyloxy, arylsulfonylC₁₋₄alkyl, arylsulfonamido, arylcarboxamido, arylsulfonamidoC₁₋₄alkyl, arylcarboxamidoC₁₋₄alkyl, aroyl, aroylC₁₋₄alkyl, or arylC₁₋₄alkanoyl group, the aryl moiety may be selected from an optionally substituted phenyl ring or an optionally substituted 5- or 6-membered heterocyclic ring. In the group R¹ an aryl moiety may be optionally substituted by one or more substituents selected from hydrogen, halogen, amino, cyano, C₁₋₄alkyl, C₁₋₄alkylamino, C₁₋₄dialkylamino, C₁₋₄alkylamido, C₁₋₄alkanoyl, or R⁶R⁷NCO where each of R⁶ and R⁷ independently represents a hydrogen atom or C₁₋₄alkyl group.

A halogen atom present in the compounds of formula (I) may be fluorine, chlorine, bromine or iodine.

When q is 2, the substituents R¹ may be the same or different.

When s is 2, the substituents R⁵ may be the same or different.

An optionally substituted 5- or 6-membered heterocyclic aromatic ring, as defined for either of the groups Ar¹ or Ar² may contain from 1 to 4 heteroatoms selected from O, N or S. When the ring contains 2-4 heteroatoms, one is preferably selected from O, N and S and the remaining heteroatoms are preferably N. Examples of 5 and 6-membered heterocyclic groups include furyl, thienyl, pyrrolyl, oxazolyl, thiazolyl, imidazolyl, oxadiazolyl, thiadiazolyl, pyridyl, triazolyl, triazinyl, pyridazyl, pyrimidinyl and pyrazolyl.

The group Ar¹ or Ar² may be optionally substituted by one or more substituents selected from: a halogen atom, or a hydroxy, oxo, cyano, nitro, C₁₋₄alkyl, C₁₋₄alkoxy, C₁₋₄alkylenedioxy, C₁₋₄alkanoyl, C₁₋₄alkylsulfonyl, C₁₋₄alkylsulfinyl, C₁₋₄alkylthio, R⁸SO₂N(R⁹)—, R⁸R⁹NSO₂—, R⁸R⁹N—, R⁸R⁹NCO—, or R⁸CON(R⁹)— group wherein each of R⁸ and R⁹ independently represents a hydrogen atom or a C₁₋₄ alkyl group, or R⁸R⁹ together form a C₃₋₆ alkylene chain.

Alternatively, Ar² may be optionally substituted by one or more 5- or 6-membered heterocyclic rings, as defined above, optionally substituted by a C₁₋₂ alkyl or R⁸R⁹N— group; wherein R⁸ and R⁹ are as defined above.

In the group Ar² substituents positioned ortho to one another may be linked to form a 5- or 6-membered ring. The group Ar may be optionally substituted by one or more substituents selected from: a halogen atom, cyano, methoxy, methylenedioxy, acetyl, acetylamino, methylsulfonyl, methylsulfonyloxy, methylaminosulfonyl, methylsulfonylamino, or methylaminocarbonyl group.

It will be appreciated that for use in medicine the salts of formula (I) should be physiologically acceptable. Suitable physiologically acceptable salts will be apparent to those skilled in the art and include for example acid addition salts formed with inorganic acids eg. hydrochloric, hydrobromic, sulfuric, nitric or phosphoric acid; and organic acids eg. succinic, maleic, acetic, fumaric, citric, tartaric, benzoic, p-toluenesulfonic, methanesulfonic or naphthalenesulfonic acid. Other non-physiologically acceptable salts eg. oxalates, may be used, for example in the isolation of compounds of formula (I) and are included within the scope of this invention. Also included within the scope of the invention are solvates and hydrates of compounds of formula (I).

Certain of the compounds of formula (I) may form acid addition salts with one or more equivalents of the acid. The present invention includes within its scope all possible stoichiometric and non-stoichiometric forms.

The compounds of formula (I) can exist in the form of cis- and trans-isomers with respect to the configuration at the cyclohexyl ring. Preferably the compounds of the invention are in the trans configuration with respect to the cyclohexyl ring.

In compounds of formula (I), it is preferred that R¹ represents a substituent selected from: a halogen atom, methyl, cyano, trifluoromethyl, pentafluoroethyl, or trifluoromethoxy group. A cyano group, for example in the 6- or 7-position of the tetrahydroisoquinoline ring, is especially preferred. Preferably q is 1. R² is preferably a hydrogen atom. In the group A, T, U, V and Y are preferably each CH, i.e. forming a phenyl ring. The group Ar² is preferably a phenyl, pyridyl, pyrimidyl or furanyl group.

Certain of the substituted heteroaromatic ring systems included in compounds of formula (I) may exist in one or more tautomeric forms. The present invention includes within its scope all such tautomeric forms, including mixtures.

Particular compounds according to the invention include those specifically exemplified and named hereinafter. These compounds may be in the form of their free base or physiologically acceptable salts thereof, particularly the monohydrochloride or monomesylate salts.

The present invention also provides a process for preparing compounds of formula (I) which process comprises:

(a) reacting a compound of formula (II):

wherein R¹, R² and q are as hereinbefore defined, with a compound of formula (III): A—COX  Formula (III) wherein A is as hereinbefore defined and X is a halogen atom or the residue of an activated ester;

(b) to prepare a compound of formula (I) wherein R¹ is Ar¹—Z and Z is a bond, reacting a compound of formula (IV):

wherein R² and A are as hereinbefore defined and one R^(1a) represents a group W wherein W is a halogen atom or a trifluoromethylsulfonyloxy group, or W is a group M selected from a boron derivative e.g. a boronic acid function B(OH)₂ or a metal function such as trialkylstannyl e.g. SnBu₃, zinc halide or magnesium halide, and when q is 2 the other R^(1a) is R¹; with a compound Ar¹—W¹, wherein W¹ is a halogen atom or a trifluoromethylsulfonyloxy group when W is a group M or W¹ is a group M when W is a halogen atom or a trifluoromethylsulfonyloxy group;

(c) to prepare a compound of formula (I) wherein R¹ is Ar¹—Z and Z is O or S, reacting a compound of formula (V):

wherein R² and A are as hereinbefore defined and one R^(1b) represents a group ZH and when q is 2 the other R^(1b) represents R¹; with a reagent serving to introduce the group Ar¹;

(d) interconversion of one compound of formula (I) to a different compound of formula (I) e.g. (i) alkylation of a compound (I) wherein R² represents hydrogen, (ii) conversion of one R¹ from alkoxy (e.g. methoxy) to hydroxy, or (iii) conversion of R¹ from hydroxy to sulfonyloxy, eg alkylsulfonyloxy or trifluoromethanesulfonyloxy;

(e) separation of cis- and trans-isomers of compounds of formula (I) by conventional methods, e.g. chromatography or crystallisation; and optionally thereafter forming a salt of formula (I).

Process (a) may be effected using conventional methods for the formation of an amide bond. When X is the residue of an activated ester this may be formed with e.g. a carbodiimide such as 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide. The reaction may be carried out in a solvent such as dichloromethane.

Reaction of a compound of formula (IV) with Ar¹W¹, according to process (b) may be effected in the presence of a transition metal eg palladium catalyst such as bis-triphenylphosphinepalladium dichloride or tetrakis-triphenylphosphinepalladium (0). When M represents a boronic acid function such as B(OH)₂the reaction may be carried out under basic conditions, for example using aqueous sodium carbonate in a suitable solvent such as dioxane. When M is trialkylstannyl the reaction may be carried out in an inert solvent, such as xylene or dioxane optionally in the presence of LiCl. When M is a zinc or magnesium halide the reaction may be effected in an aprotic solvent such as tetrahydrofuran. The substituent W is preferably a halogen atom such as bromine, or a sulfonyloxy group such as trifluoromethylsulfonyloxy; and W¹ is preferably a goup M, such as trialkylstannyl or B(OH)₂.

In process (c) the reagent serving to introduce the group Ar¹ is preferably a compound of formula Ar¹—Hal, wherein Hal is a halogen atom. The reaction may be effected in the presence of a base, such as potassium carbonate, in a solvent such as dimethylformamide.

Interconversion reactions according to process (d) may be effected using methods well known in the art.

Compounds of formula (II) may be prepared by conversion of a compound of formula (VI), wherein R¹ and q are as hereinbefore defined,

into a corresponding ketone, followed by reductive amination. This may be effected by methods well known in the art for (i) conversion of a ketal to a ketone in the presence of aqueous acid; followed by (ii) reductive amination of the ketone with R²NH₂ or ammonium acetate in the presence of a reducing agent. Suitable reducing agents which may be employed include sodium borohydride, cyanoborohydride or triacetoxyborohydride under acidic conditions, or catalytic hydrogenation. The reaction may conveniently be effected in a solvent such as methanol, ethanol or dichloroethane.

A compound of formula (VI) may itself be prepared by reacting a compound of formula (VII):

wherein R¹ and q are as hereinbefore defined; with a compound of formula (VIII):

in the presence of a reducing agent. Suitable reducing agents which may be employed include sodium borohydride, cyanoborohydride or triacetoxyborohydride under acidic conditions, or catalytic hydrogenation. The reaction may conveniently be effected in a solvent such as ethanol or dichloroethane.

The individual cis- and trans-isomers of a compound of formula (II) may be prepared starting from cis- or trans-4-amino-cyclohexaneacetic acid (T. P. Johnson, et al., J. Med. Chem., 1997, (20), 279-290) followed by functional group interchange and/or protection using methods well known in the art, to give the individual cis- or trans-isomers of a compound of formula (IX):

wherein R² is as hereinbefore defined, and P is a protecting group, for example trifluoroacetyl or tert-butoxycarbonyl. Subsequent reaction of a compound of formula (IX) with a compound of formula (VII) in the presence of a reducing agent as described above followed by deprotection using standard methodology gives the individual isomers of a compound of formula (II) wherein R² is as hereinbefore defined.

Compounds of formula (III) are known or may be prepared using standard procedures.

Compounds of formula (IV) or (V) may be prepared by processes analogous to (a), (b) and (c) described above. Compounds Ar¹W¹ and Ar¹Hal are commercially available or may be prepared by standard methods. Compounds of formula (VII) are known in the literature or may be prepared by known methods. The compound of formula (VIII) is likewise known in the literature.

Compounds of formula (I) have been found to exhibit affinity for dopamine receptors, in particular the D₃ receptor, and are expected to be useful in the treatment of disease states which require modulation of such receptors, such as psychotic conditions. Compounds of formula (I) have also been found to have greater affinity for dopamine D₃ than for D₂ receptors. The therapeutic effect of currently available antipsychotic agents (neuroleptics) is generally believed to be exerted via blockade of D₂ receptors; however this mechanism is also thought to be responsible for undesirable extrapyramidal side effects (eps) associated with many neuroleptic agents. Without wishing to be bound by theory, it has been suggested that blockade of the recently characterised dopamine D₃ receptor may give rise to beneficial antipsychotic activity without significant eps. (see for example Sokoloff et al, Nature, 1990; 347: 146-151; and Schwartz et al, Clinical Neuropharmacology, Vol 16, No. 4, 295-314, 1993). Preferred compounds of the present invention are therefore those which have higher affinity for dopamine D₃ than dopamine D₂ receptors (such affinity can be measured using standard methodology for example using cloned dopamine receptors). Said compounds may advantageously be used as selective modulators of D₃ receptors.

We have found that certain compounds of formula (I) are dopamine D₃ receptor antagonists, others may be agonists or partial agonists. The functional activity of compounds of the invention (i.e. whether they are antagonists, agonists or partial agonists) can be readily determined using the test method described hereinafter, which does not require undue experimentation. D₃ antagonists are of potential use as antipsychotic agents for example in the treatment of schizophrenia, schizo-affective disorders, psychotic depression, mania, paranoid and delusional disorders. Furthermore, they could have utility as adjunct therapy in Parkinsons Disease, particularly with compounds such as L-DOPA and possibly dopaminergic agonists, to reduce the side effects experienced with these treatments on long term use (eg see Schwartz et al., Brain Res. Reviews, 1998, 26, 236-242). From the localisation of D3 receptors, it could also be envisaged that D3 antagonists could also have utility for the treatment of substance abuse where it has been suggested that D3 receptors are involved (eg see Levant, 1997, Pharmacol. Rev., 49, 231-252). Conditions which may be treated by dopamine D₃ receptor agonists include dyskinetic disorders such as Parkinson's disease, neuroleptic-induced parkinsonism and tardive dyskinesias; depression; anxiety, memory disorders, sexual dysfunction and drug (eg. cocaine) dependency.

In a further aspect therefore the present invention provides a method of treating conditions which require modulation of dopamine D₃ receptors, for example psychoses such as schizophrenia, which comprises administering to a subject in need thereof an effective amount of a compound of formula (I) or a physiologically acceptable salt thereof.

The invention also provides the use of a compound of formula (I) or a physiologically acceptable salt thereof in the manufacture of a medicament for the treatment of conditions which require modulation of dopamine D₃ receptors, for example psychoses such as schizophrenia.

A preferred use for D₃ antagonists according to the present invention is in the treatment of psychoses such as schizophrenia.

A preferred use for D₃ agonists according to the present invention is in the treatment of dyskinetic disorders such as Parkinson's disease.

For use in medicine, the compounds of the present invention are usually administered as a standard pharmaceutical composition. The present invention therefore provides in a further aspect pharmaceutical compositions comprising a novel compound of formula (I) or a physiologically acceptable salt thereof and a physiologically acceptable carrier.

The compounds of formula (I) may be administered by any convenient method, for example by oral, parenteral, buccal, sublingual, nasal, rectal or transdermal administration and the pharmaceutical compositions adapted accordingly.

The compounds of formula (I) and their physiologically acceptable salts which are active when given orally can be formulated as liquids or solids, for example syrups, suspensions or emulsions, tablets, capsules and lozenges.

A liquid formulation will generally consist of a suspension or solution of the compound or physiologically acceptable salt in a suitable liquid carrier(s) for example an aqueous solvent such as water, ethanol or glycerine, or a non-aqueous solvent, such as polyethylene glycol or an oil. The formulation may also contain a suspending agent, preservative, flavouring or colouring agent.

A composition in the form of a tablet can be prepared using any suitable pharmaceutical carrier(s) routinely used for preparing solid formulations. Examples of such carriers include magnesium stearate, starch, lactose, sucrose and cellulose.

A composition in the form of a capsule can be prepared using routine encapsulation procedures. For example, pellets containing the active ingredient can be prepared using standard carriers and then filled into a hard gelatin capsule; alternatively, a dispersion or suspension can be prepared using any suitable pharmaceutical carrier(s), for example aqueous gums, celluloses, silicates or oils and the dispersion or suspension then filled into a soft gelatin capsule.

Typical parenteral compositions consist of a solution or suspension of the compound or physiologically acceptable salt in a sterile aqueous carrier or parenterally acceptable oil, for example polyethylene glycol, polyvinyl pyrrolidone, lecithin, arachis oil or sesame oil. Alternatively, the solution can be lyophilised and then reconstituted with a suitable solvent just prior to administration.

Compositions for nasal administration may conveniently be formulated as aerosols, drops, gels and powders. Aerosol formulations typically comprise a solution or fine suspension of the active substance in a physiologically acceptable aqueous or non-aqueous solvent and are usually presented in single or multidose quantities in sterile form in a sealed container, which can take the form of a cartridge or refill for use with an atomising device. Alternatively the sealed container may be a unitary dispensing device such as a single dose nasal inhaler or an aerosol dispenser fitted with a metering valve which is intended for disposal once the contents of the container have been exhausted. Where the dosage form comprises an aerosol dispenser, it will contain a propellant which can be a compressed gas such as compressed air or an organic propellant such as a fluoro-chlorohydrocarbon. The aerosol dosage forms can also take the form of a pump-atomiser.

Compositions suitable for buccal or sublingual administration include tablets, lozenges and pastilles, wherein the active ingredient is formulated with a carrier such as sugar and acacia, tragacanth, or gelatin and glycerin.

Compositions for rectal administration are conveniently in the form of suppositories containing a conventional suppository base such as cocoa butter.

Compositions suitable for transdermal administration include ointments, gels and patches.

Preferably the composition is in unit dose form such as a tablet, capsule or ampoule.

Each dosage unit for oral administration contains preferably from 1 to 250 mg (and for parenteral administration contains preferably from 0.1 to 25 mg) of a compound of the formula (I) or a physiologically acceptable salt thereof calculated as the free base.

The physiologically acceptable compounds of the invention will normally be administered in a daily dosage regimen (for an adult patient) of, for example, an oral dose of between 1 mg and 500 mg, preferably between 10 mg and 400 mg, e.g. between 10 and 250 mg or an intravenous, subcutaneous, or intramuscular dose of between 0.1 mg and 100 mg, preferably between 0.1 mg and 50 mg, e.g. between 1 and 25 mg of the compound of the formula (I) or a physiologically acceptable salt thereof calculated as the free base, the compound being administered 1 to 4 times per day. Suitably the compounds will be administered for a period of continuous therapy, for example for a week or more.

Biological Test Methods

The ability of the compounds to bind selectively to human D₃ dopamine receptors can be demonstrated by measuring their binding to cloned receptors. The inhibition constants (K_(i)) of test compounds for displacement of [¹²⁵I] iodosulpride binding to human D₃ dopamine receptors expressed in CHO cells were determined as follows. The cell lines were shown to be free from bacterial, fungal and mycoplasmal contaminants, and stocks of each were stored frozen in liquid nitrogen. Cultures were grown as monolayers or in suspension in standard cell culture media. Cells were recovered by scraping (from monolayers) or by centrifugation (from suspension cultures), and were washed two or three times by suspension in phosphate buffered saline followed by collection by centrifugation. Cell pellets were stored frozen at −40° C. Crude cell membranes were prepared by homogenisation followed by high-speed centrifugation, and characterisation of cloned receptors achieved by radioligand binding.

Preparation of CHO Cell Membranes

Cell pellets were gently thawed at room temperature, and resuspended in about 20 volumes of ice-cold 50 mM Tris salts (pH 7.4 @ 37° C.), 20 mM EDTA, 0.2 M sucrose. The suspension was homogenised using an Ultra-Turrax at full speed for 15 sec. The homogenate was centrifuged at 18,000 r.p.m for 20 min at 4° C. in a Sorvall RC5C centrifuge. The membrane pellet was resuspended in ice-cold 50 mM Tris salts (pH 7.4 @ 37° C.), using an Ultra-Turrax, and recentrifuged at 18,000 r.p.m for 15 min at 4° C. in a Sorvall RC5C. The membranes were washed two more times with ice-cold 50 mM Tris salts (pH 7.4 @ 37° C.). The final pellet was resuspended in 50 mM Tris salts (pH 7.4 @ 37° C.), and the protein content determined using bovine serum albumin as a standard (Bradford, M. M. (1976) Anal. Biochem. 72, 248-254).

Binding Experiments on Cloned Dopamine Receptors

Crude cell membranes were incubated with 0.1 nM [¹²⁵I] iodosulpride (˜2000 Ci/mmol; Amersham, U. K.), and the test compound in a buffer containing 50 mM Tris salts (pH 7.4 @ 37° C.), 120 mM NaCl, 5 mM KCl, 2 mM CaCl₂, 1 mM MgCl₂, 0.1% (w/v) bovine serum albumin, in a total volume of 1 ml for 30 min at 37° C. Following incubation, samples were filtered using a Brandel Cell Harvester, and washed three times with ice-cold 50 mM Tris salts (pH 7.4 @ 37° C.), 120 mM NaCl, 5 mM KCl, 2 mM CaCl₂, 1 mM MgCl₂. The radioactivity on the filters was measured using a Cobra gamma counter (Canberra Packard). Non-specific binding was defined as the radioligand binding remaining after incubation in the presence of 100 μM iodosulpride. For competition curves, 14 concentrations (half-log dilutions) of competing cold drug were used. Competition curves were analysed simultaneously whenever possible using non-linear least-squares fitting procedures, capable of fitting one, two or three site models.

Functional Activity at Cloned Dopamine Receptors

The functional activity of compounds at human D2 and human D3 receptors (ie agonism or antagonism) may be determined using a Cytosensor Microphysiometer (McConnell H M et al Science 1992 257 1906-1912) In Microphysiometer experiments, cells (hD2_CHO or hD3_CHO) were seeded into 12 mm Transwell inserts (Costar) at 300000 cells/cup in foetal calf serum (FCS)-containing medium. The cells were incubated for 6 h at 37° C. in 5% CO₂, before changing to FCS-free medium. After a further 16-18 h, cups were loaded into the sensor chambers of the Cytosensor Microphysiometer (Molecular Devices) and the chambers perfused with running medium (bicarbonate-free Dulbecco's modified Eagles medium containing 2 mM glutamine and 44 mM NaCl) at a flow rate of 100 ul/min. Each pump cycle lasted 90 s. The pump was on for the first 60 s and the acidification rate determined between 68 and 88 s, using the Cytosoft programme. Test compounds were diluted in running medium. In experiments to determine agonist activity, cells were exposed (4.5 min for hD2, 7.5 min for hD3) to increasing concentrations of putative agonist at half hour intervals. Seven concentrations of the putative agonist were used. Peak acidification rate to each putative agonist concentration was determined and concentration-response curves fitted using Robofit [Tilford, N. S., Bowen, W. P. & Baxter, G. S. Br. J. Pharmacol. (1995) in press]. In experiments to determine antagonist potency, cells were treated at 30 min intervals with five pulses of a submaximal concentration of quinpirole (100 nM for hD2 cells, 30 nM for hD3 cells), before exposure to the lowest concentration of putative antagonist. At the end of the next 30 min interval, cells were pulsed again with quinpirole (in the continued presence of the antagonist) before exposure to the next highest antagonist concentration. In all, five concentrations of antagonist were used in each experiment. Peak acidification rate to each agonist concentration was determined and concentration-inhibition curves fitted using Robofit.

Pharmaceutical Formulations

The following represent typical pharmaceutical formulations according to the present invention, which may be prepared using standard methods.

IV Infusion Compound of formula (I) 1-40 mg Buffer to pH ca 7 Solvent/complexing agent to 100 ml Bolus Injection Compound of formula (I) 1-40 mg Buffer to pH ca 7 Co-Solvent to 5 ml Buffer: Suitable buffers include citrate, phosphate, sodium hydroxide/hydrochloric acid. Solvent: Typically water but may also include cyclodextrins (1-100 mg) and co-solvents such as propylene glycol, polyethylene glycol and alcohol.

Tablet Compound 1-40 mg Diluent/Filler* 50-250 mg Binder 5-25 mg Disentegrant* 5-50 mg Lubricant 1-5 mg Cyclodextrin 1-100 mg *may also include cyclodextrins Diluent: e.g. Microcrystalline cellulose, lactose, starch Binder: e.g. Polyvinylpyrrolidone, hydroxypropymethylcellulose Disintegrant: e.g. Sodium starch glycollate, crospovidone Lubricant: e.g. Magnesium stearate, sodium stearyl fumarate.

Oral Suspension Compound 1-40 mg Suspending Agent 0.1-10 mg Diluent 20-60 mg Preservative 0.01-1.0 mg Buffer to pH ca 5-8 Co-solvent 0-40 mg Flavour 0.01-1.0 mg Colourant 0.001-0.1 mg Suspending agent:e.g. Xanthan gum, microcrystalline cellulose Diluent: e.g. sorbitol solution, typically water Preservative: e.g. sodium benzoate Buffer: e.g. citrate Co-solvent: e.g. alcohol, propylene glycol, polyethylene glycol, cyclodextrin

The invention is further illustrated by the following non-limiting examples:

DESCRIPTION 1

6-Cyano-1,2,3,4-tetrahydroisoquinoline

Prepared in a similar manner to that described in H. G. Selnick et al., Synthetic Communications 25 (20) 3255 (1995).

Mass spectrum (API⁺): Found 159 (MH⁺). C₁₀H₁₀N₂ requires 158.

¹H NMR (CDCl₃) δ: 2.47 (1H, br s), 2.82 (2H, m), 3.15 (2H, m), 4.05 (2H, s), 7.10 (1H, d, J=8 Hz), 7.40 (2H, m).

DESCRIPTION 2

trans-2-(1-(4-(N-tert-Butyloxycarbonyl)amino)cyclohexyl)acetic acid, methyl ester

A mixture of trans-(4-amino)cyclohexylactic acid hydrogen sulfate (T. P. Johnston et al; J. Med Chem., 1977, 20 (2), 279-290), (27.0 g, 106 mmol), conc. H₂SO₄ (3 ml), and methanol (300 ml) was stirred at reflux for 5 h. Resulting solution was filtered and the filtrate evaporated in vacuo to give a brown oil (36 g). A mixture of this material, triethylamine (36 ml; 26.1 g, 259 mmol), dichloromethane (600 ml) and di-t-butyl dicarbonate (25.5 g, 117 mmol) was stirred at 20° C. for 18 h. Resulting solution was partitioned between saturated aqueous NaHCO₃ (500 ml) and dichloromethane (3×200 ml), and the combined extracts were dried (Na₂SO₄) and evaporated in vacuo to give the title compound (24.6 g, 86%) as a colourless solid.

¹H NMR (CDCl₃) δ: 1.08 (4H, m), 1.43 (9H, s), 1.76 (3H, m), 2.00 (2H, m), 2.20 (2H, d, J=7 Hz), 3.37 (1H, m), 3.66 (3H, s), 4.39 (1H, br s).

DESCRIPTION 3

trans-2-(1-(4-(N-tert-Butyloxycarbonyl)amino)cyclohexyl)acetaldehyde

To a stirred solution of trans-2-(1-(4-(N-tert-butyloxycarbonyl)amino)cyclohexyl)acetic acid, methyl ester (46.0 g, 170 mmol) in dry toluene (920 ml) at −78° C. under argon was added a solution of di-isobutylaluminium hydride (1M; 285 ml; 285 mmol), dropwise over 0.5 h. Resulting solution was stirred for a further 0.3 h and quenched with a mixture of methanol (28 ml) in toluene (50 ml) and then poured into saturated aqueous potassium sodium tartrate (1.2L). The resultant mixture was extracted with ether (4×1L). The combined organic extracts were dried (Na₂SO₄) and evaporated in vacuo to give a waxy solid which was purified using silica gel, eluting with 10-50% ethyl acetate/hexane to give the title compound (21.77 g, 53%) as a colourless solid.

¹H NMR (CDCl₃) δ: 1.12 (4H, m), 1.44(9H, s), 1.78 (3H, m), 2.00(2H, m), 2.33 (2H, dd, J=7,2 Hz), 3.37 (1H, m), 4.40 (1H, m), 9.75 (1H, m).

DESCRIPTION 4

trans-2-(2-(1-(4-(N-tert-Butyloxycarbonyl)amino)cyclohexyl)ethyl)-6-cyano-1,2,3,4-tetrahydroisoquinoline

A mixture of trans-2-(1-(4-(N-tert-butyloxycarbonyl)amino)cyclohexyl)acetaldehyde (6.0 g, 24.9 mmol), 6-cyano-1,2,3,4-tetrahydroisoquinoline (3.93 g, 24.9 mmol), sodium triacetoxyborohydride (7.7 g, 36.3 mmol) in 1,2-dichloroethane (270 ml) was stirred at 20° C. for 16 h. Resulting solution was partitioned between aqueous K₂CO₃ (200 ml) and dichloromethane (100 ml), and the combined extracts were washed with brine (200 ml), dried (Na₂SO₄) and evaporated in vacuo to a minimum volume and filtered through a pad of silica (100 g), washing with ethyl acetate. The filtrate was evaporated in vacuo to give the title compound (8.33 g, 87%) as a yellow solid.

¹H NMR (CDCl₃) δ: 1.08 (4H, m), 1.28 (1H, m), 1.44 (9H, s), 1.48 (2H, m), 1.78 (2H, m), 1.99 (2H, m), 2.52 (2H, m), 2.72 (2H, t, J=7 Hz), 2.91 (2H, ,m), 3.37 (1H, m), 3.63 (2H, m), 4.40 (1H, m), 7.12 (1H, d, J=8 Hz), 7.39 (2H, m).

DESCRIPTION 5

trans-2-(2-(1-(4-Amino)cyclohexyl)ethyl)-6-cyano-1,2,3,4-tetrahydroisoquinoline

A mixture of trans-2-(2-(1-(4-(N-tert-butyloxycarbonyl)amino)cyclohexyl)ethyl)-6-cyano-1,2,3,4-tetrahydroisoquinoline (8.3 g, 21.7 mmol), trifluoroacetic acid (15 ml) and dichloromethane (180 ml) was stirred at 20° C. for 2 h. Resulting solution was evaporated in vacuo and the residue partitioned between saturated aqueous K₂CO₃ (200 ml) and dichloromethane (2×100 ml). The combined organic extracts were washed with brine (100 ml), dried (Na₂SO₄) and evaporated in vacuo to give the title compound (4.99 g, 81%) as a brown oil.

Mass spectrum (API⁺): Found 284 (MH⁺). C₁₈H₂₅N₃ requires 283.

¹H NMR (CDCl₃) δ: 0.91-1.16 (4H, m), 1.22-1.40 (3H, m), 1.47 (2H, m), 1.72-1.91 (4H, m), 2.52 (2H, m), 2.59 (1H, m), 2.72 (2H, t, J=7 Hz), 2.92 (2H, m), 3.64 (2H, s), 7.11 (1H, d, J=8 Hz),7.39(2H, m).

DESCRIPTION 6

6-Cyano-1,2,3,4-tetrahydroisoquinoline hydrochloride

As an alternative procedure to that contained within Description 1, a solution of 6-bromo-1,2,3,4-tetrahydroisoquinoline hydrochloride (6.0 g, 24 mmol) and triethylamine (7.4 ml, 5.36 g, 53 mmol) in dichloromethane (100 ml) was treated with trifluoroacetic anhydride (3.7 ml, 5.54 g, 26.4 mmol) with ice cooling. Mixture was stirred at 20° C. for 1.5 h. then partitioned between saturated aqueous NaHCO₃ (250 ml) and dichloromethane (3×50 ml). Combined organic extracts were dried (Na₂SO₄) and evaporated in vacuo to give a solid (8.3 g). A mixture of the latter with copper (I) cyanide (5.1 g, 56.6 mmol) in 1-methyl-2-pyrrolidinone (100 ml) was heated at reflux under argon for 4 h, then cooled and partitioned between water (300 ml), 0.880 aqueous ammonia (100 ml) and dichloromethane (5×200 ml). Combined organic extracts were dried (Na₂SO₄) and evaporated in vacuo to give an oil. The latter was dissolved in ether and treated with ethereal HCl to give the title compound (4.47 g, 85%) as a colourless solid.

Mass spectrum (API⁺): Found 159 (MH⁺). C₁₀H₁₀N₂ requires 158.

EXAMPLE 1

trans-6-Cyano-2-[2-(1-(4-(3-(4-pyridyl)benzamido))cyclohexyl)ethyl]-1,2,3,4-tetrahydroisoquinoline

A mixture of trans-2-(2-(1-(4-amino)cyclohexyl)ethyl)-6-cyano-1,2,3,4-tetrahydroisoquinoline (0.1 g: 0.35 mmol), 3-(4-pyridyl)benzoic acid (0.070 g; 0.35 mmol), 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (0.067 g; 0.35 mmol), 1-hydroxybenzotriazole (catalytic amount) and dichloromethane (4 ml) was shaken for 16 h. Saturated aqueous sodium bicarbonate (4 ml) was added and the mixture shaken for 0.25 h. Chromatography of the organic layer on silica eluting with 30-100% ethyl acetate in hexane and 0-10% methanol in ethyl acetate gradient elution gave the title compound (0.075 g; 46%) as a yellow solid.

Mass spectrum (API⁺): Found 465 (MH⁺). C₃₀H₃₂N₄O requires 464.

¹H NMR (CDCl₃) δ: 1.00-1.30 (5H, m), 1.40-1.60 (2H, m), 1.75-1.95 (2H, m), 2.00-2.20 (2H, m), 2.50-2.60 (2H, m), 2.70-2.75 (2H, m), 2.90-2.94 (2H, m), 3.65 (2H, s), 3.95 (1H, m), 6.29(1H, d, J=8 Hz), 7.11 (1H, d, J=8 Hz), 7.36-7.39(2H, m), 7.45-7.56 (3H, m), 7.73 (1H, d, J=8 Hz), 7.79 (1H, d, J=8 Hz), 8.05 (1H, s) and 8.65 (2H, d, J=6 Hz).

The following compounds were prepared according to the procedure of Example 1

Ex- Characterising Data am- Mass spectrum (API⁺) ¹H ple A NMR δ (CDCl₃ or d₆-DMSO) 2

MH⁺ 465. C₃₀H₃₂N₄O requires 464 1.10-140(5H, m), 1.40-1.60 (2H, m), 1.80-1.90(2H, m), 2.10-2.20(2H, m), 2.50-2.60 (2H, m), 2.70-2.76(2H, m), 2.90-2.95(2H, m), 3.65(2H, s), 3.96(1H, m), 6.01(1H, d, J=8Hz), 7.12(1H, d, J=8Hz), 7.25-7.40(3H, m), 7.54(1H, t, J=8Hz), 7.68-7.76(2H, m), 7.89-7.97(1H, m), 7.97(1H, m), 8.62(1H, dd, J=5 and 1.5Hz) and 8.86(1H, d, J=2Hz) 3

MH⁺ 466. C₂₉H₃₁N₅O requires 465. 1.10-1.40(5H, m), 1.40- 1.60(2H, m), 1.80-1.95(2H, m), 2.10-2.16(2H, m), 2.53- 2.59(2H, m), 2.71-2.76(2H, m), 2.90-3.00(2H, m), 3.65(2H, s), 3.97(1H, m), 6.01(1H, d, J= 8Hz), 7.12(1H, d, J=8Hz), 7.35- 7.41(2H, m), 7.85(1H, t, J= 8Hz), 7.70(1H, m), 7.80(1H, m), 8.01(1H, m), 8.98(2H, s) and 9.24(1H, s). 4

MH⁺ 454. C₂₉H₃₁N₃O₂ requires 453. 1.10-1.40(5H, m), 1.45- 1.60(2H, m), 1.80-1.90(2H, m), 2.10-2.15(2H, m), 2.50-2.60 (2H, m), 2.70-2.76(2H, m), 2.90-2.95(2H, m), 3.65(2H, s), 3.95(1H, m), 5.98(1H, d, J= 8Hz), 6.49(1H, dd, J=3 and 2Hz), 6.74(1H, d, J=3Hz), 7.12(1H, d, J=8Hz), 7.38-7.50 (4H, m), 7.61(1H, d. J=8Hz), 7.78(1H, d, J=8Hz) and 8.03(1H, s). 5

MH⁺ 464. C₃₁H₃₃N₃O requires 463. 1.10-1.40(5H, m), 1.45- 1.60(2H, m), 1.84-1.88(2H, m), 2.10-2.15(2H, m), 2.50- 2.60(2H, m), 2.70-2.75(2H, m), 2.90-2.95(2H, m), 3.65(2H, s), 3.95(1H, s), 5.97(1H, d, J=8Hz), 7.12(1H, d, J=8 Hz), 7.25-7.52 (6H, m), 7.60(2H, m), 7.70(2H, m) and 7.96(1H, s) 6

MH⁺ 464. C₃₁H₃₃N₃O requires 463. 0.60-0.74(2H, m), 0.85- 1.15(3H, m), 1.40-1.50(2H, m), 1.66-1.90(4H, m), 2.38-2.50 (2H, m), 2.66-2.71(2H, m), 2.87-2.91(2H, m), 3.60(2H, s), 3.68(1H, m), 4.99(1H, d, J= 8Hz), 7.12(1H, d, J=8Hz), 7.30- 7.50(10H, m) and 7.71(1H, m). 7

MH⁺ 479. C₃₁H₃₄N₄O requires 478. 1.10-1.40(5H, m), 1.40- 1.60(2H, m), 1.80-1.90(2H, m), 2.10-2.20(2H, m), 2.50-2.60 (2H, m), 2.63(3H, s), 2.70-2.76 (2H, m), 2.90-2.95(2H, m), 3.71 (2H, s), 3.98(1H, m), 6.03(1H, d, J=8Hz), 7.10(1H, d, J=8Hz), 7.33(1H, d, J=5Hz), 7.35-7.41 (3H, m), 7.53(1H, t, J=8Hz), 7.72-7.77 (2H, m), 8.02(1H, s) and 8.56 (1H, d, J=5Hz) 

1. A compound of formula (I):

wherein: R¹ represents a substituent selected from: a hydrogen or halogen atom; a hydroxy, cyano, nitro, trifluoromethyl, trifluoromethoxy, trifluoromethanesulfonyloxy, pentafluoroethyl, C₁₋₄alkyl, C₁₋₄alkoxy, arylC₁₋₄alkoxy, C₁₋₄alkylthio, C₁₋₄alkoxyC₁₋₄alkyl, C₃₋₆cycloalkylC₁₋₄alkoxy, C₁₋₄alkanoyl, C₁₋₄alkoxycarbonyl, C₁₋₄alkylsulfonyl, C₁₋₄alkylsufonyloxy, C₁₋₄alkylsulfonylC₁₋₄alkyl, arylsulfonyl, arylsulfonyloxy, arylsulfonylC₁₋₄alkyl, C₁₋₄alkylsulfonamido, C₁₋₄alkylamido, C₁₋₄alkylsulfonamidoC₁₋₄alkyl, C₁₋₄alkylamidoC₁₋₄alkyl, arylsulfonamido, arylcarboxamido, arylsulfonamidoC₁₋₄alkyl, arylcarboxamidoC₁₋₄alkyl, aroyl, aroylC₁₋₄alkyl, or arylC₁₋₄alkanoyl group; a group R³OCO(CH₂)_(p), R³CON(R⁴)(CH₂)_(p), R³R⁴NCO(CH₂)_(p) or R³R⁴NSO₂(CH₂)_(p) where each of R³ and R⁴ independently represents a hydrogen atom or a C₁₋₄alkyl group or R³R⁴ forms part of a C₃₋₆azacyloalkane or C₃₋₆(2-oxo)azacycloalkane ring and p represents zero or an integer from 1 to 4; or a group Ar¹—Z, wherein Ar¹ represents an optionally substituted phenyl ring or an optionally substituted 5- or 6-membered aromatic heterocyclic ring and Z represents a bond, O, S , or CH₂; R² represents a hydrogen atom or a C₁₋₄alkyl group; q is 1 or 2; A represents a group of formula (a) or (b)

wherein T, U, V and Y independently represent CH or a nitrogen atom; R⁵ is a group selected from: a hydrogen or halogen atom, cyano, C₁₋₄ alkyl or C₁₋₄ alkoxy group s is 1 or 2; Ar² represents an optionally substituted phenyl ring or an optionally substituted 5- or 6-membered aromatic heterocyclic ring; or a salt thereof.
 2. A compound or salt as claimed in claim 1 wherein q represents
 1. 3. A compound or salt as claimed in claim 1, wherein the group Ar¹ or Ar² is optionally substituted by one or more substituents selected from: a halogen atom, or a hydroxy, oxo, cyano, nitro, C₁₋₄alkyl, C₁₋₄alkoxy, C₁₋₄alkylenedioxy, C₁₋₄alkanoyl, C₁₋₄alkylsulfonyl, C₁₋₄alkylsulfinyl, C₁₋₄alkylthio, R⁸SO₂N(R⁹)—, R⁸R⁹NSO₂, R⁸R⁹N—, R⁸R⁹NCO—, or R⁸CON(R9)- group or Ar² is optionally substituted by one or more 5- or 6-membered aromatic heterocyclic rings optionally substituted by a C₁₋₂ alkyl or R⁸R⁹N— group; wherein each R⁸ and R⁹ independently represents a hydrogen atom or a C₁₋₄ alkyl group, or R⁸R⁹ together form a C₃₋₆ alkylene chain.
 4. A compound or salt as claimed in claim 1, wherein T, U, V and Y are each CH, thus forming a phenyl ring in group A.
 5. A compound selected from: trans-6-Cyano-2-[2-(1-(4-(3-(4-pyridyl)benzamido))cyclohexyl)ethyl]-1,2,3,4-tetrahydroisoquinoline, trans-6-Cyano-2-[2-(1-(4-(3-(3-pyridyl)benzamido))cyclohexyl)ethyl]-1,2,3,4-tetrahydroisoquinoline, trans-6-Cyano-2-[2-(1-(4-(3-(5-pyrimidinyl)benzamido))cyclohexyl)ethyl]-1,2,3,4-tetrahydroisoquinoline, trans-6-Cyano-2-[2-(1-(4-(3-(2-furyl)benzamido))cyclohexyl)ethyl]-1,2,3,4-tetrahydroisoquinoline, trans-6-Cyano-2-[2-(1-(4-(3-(phenyl)benzamido))cyclohexyl)ethyl]-1,2,3,4-tetrahydroisoquinoline, trans-6-Cyano-2-[2-(1-(4-(2-(phenyl)benzamido))cyclohexyl)ethyl]-1,2,3,4-tetrahydroisoquinoline, trans-6-Cyano-2-[2-(1-(4-(3-(2-methyl-4-pyridyl)benzamido))cyclohexyl)ethyl]-1,2,3,4-tetrahydroisoquinoline, or a salt thereof.
 6. A process for preparing a compound or salt of formula (I) which process comprises: (a) reacting a compound of formula (II):

wherein R¹, R², and q are as defined in claim 1, with a compound of formula (III): A—COX  Formula (III) wherein A is as defined in claim 1, and X is a halogen atom or the residue of an activated ester; or (b) preparing a compound of formula (I) wherein R¹ is Ar¹—Z and Z is a bond, reacting a compound of formula (IV):

wherein R², and A are as defined in claim 1, one R^(1a) represents a group W wherein W is a halogen atom or a trifluoromethylsulfonyloxy group, or W is a group M selected from a boron derivative or a metal function, and when q is 2 the other R^(1a) is R¹ as defined in claim 1; with a compound Ar¹—W¹, wherein W¹ is a halogen atom or a trifluoromethylsulfonyloxy group when W is a group M, or W¹ is a group M as defined above when W is a halogen atom or a trifluoromethylsulfonyloxy group; or (c) preparing a compound of formula (I) wherein R¹ is Ar¹—Z and Z is O or S, reacting a compound of formula (V):

wherein R² and A are as defined in claim 1, one R^(1b) represents a group ZH and when q is 2 the other R^(1b) represents R¹ as defined in claim 1; with a reagent serving to introduce the group Ar¹; or (d) interconverting one compound of formula (I) to a different compound of formula (I) by (i) alkylation of a compound (I) wherein R² represents hydrogen, (ii) conversion of one R¹ from alkoxy to hydroxy, or (iii) conversion of R¹ from hydroxy to sulfonyloxy; or (e) separating cis- and trans-isomers of compounds of formula (I) by conventional methods; and optionally thereafter forming a salt of formula (I).
 7. A pharmaceutical composition comprising a compound of formula (I) as defined in claim 1 or a physiologically acceptable salt thereof and a physiologically acceptable carrier therefor.
 8. A method of treating depression and anxiety conditions which require modulation of a dopamine D₃ receptor which comprises administering to a subject in need thereof an effective amount of a compound of formula (I) as claimed in claim 1 or a physiologically acceptable salt thereof.
 9. The method as claimed in claim 8 wherein a dopamine D₃ antagonist is required. 